Rumsfeld gave the administration's reasoning during testimony before the House Armed Services Committee.

The administration sent a supplemental request to Congress Feb. 14 for almost $90 billion, most of which is earmarked for Iraq and Afghanistan operations. Aside from the supplemental request, the administration has asked Congress for $419.3 billion in Defense Department funding for fiscal 2006.

The secretary said a key part of the separate requests is simply the length of time it takes to put a budget together. It takes Pentagon officials up to a year to put together a budget request, he said. So, for example, the fiscal 2006 defense budget request has just been presented to Congress, while officials already are working on the fiscal 2007 request.

Once the Pentagon comes up with a proposal, it has to be cleared through the Office of Management and Budget. The president approves the request and then presents it to Congress. Congress can take eight to 10 months to pass the request, and "then it takes 12 months after that to execute it," the secretary said. This can mean a period of some two and a half years.

"In war, circumstances on the ground can change quickly, and what was not an urgent necessity at one point in a conflict can prove to be urgent in the next, as the enemy's strategy shifts and as new challenges arise," Rumsfeld said.

Officials prepare supplemental appropriations which used to be called emergency supplemental appropriations much closer to the time they are needed. The secretary said this allows for more accuracy in assessing actual costs and quicker access to the needed funds.